In conventional trim dies for battery grid-casting machines, as shown, for example, in U.S. Pat. No. 2,638,982, the leading and trailing ends of each grid plate are trimmed simultaneously by a pair of knives fixed to a common movable die member. Because the distance between these two trim knives is fixed, such prior trim dies can only be used for trimming plates of one size. When a larger or smaller grid plate is cast, the trim die must be changed to accomodate the change in plate size. This requires the shut down of the battery grid-casting machine for a long period of time, and consequently results in the loss of valuable production time. This also requires that two or three sets of very expensive dies be kept on hand for each grid-casting machine, and usually a battery manufacturing plant will have at least several such machines.
Another problem with prior trim dies is caused by the fact that the grid plates are fed by gravity into the die. A plate will sometimes hang up in its gravity feed path because of slight imperfections in the plate or path, and therefore the plate may not be fully inserted into the die before the die closes, or the plate may not be inserted squarely into the die, resulting in either case in an imperfectly trimmed plate which must be discarded.
In prior trim dies the plate to be trimmed is supported on a stationary die block between the pair of trim knives. Because the knives trim the opposite ends of each lead plate simultaneously, and lead tends to cut "tight", the trimmed plate can become wedged between the knives, causing problems in ejecting the plate from the die after trimming.
Accordingly, there is a need for an improved method and apparatus for trimming grid plate castings which will avoid the foregoing problems of prior trimming methods and apparatus.